Several developers released new Facebook-integrated mobile web apps today to coincide with the launch of Facebook’s mobile application platform. The Huffington Post, Flixster, AudioVroom and others provide an early showcase of the potential of the platform, including the ability to integrate with a mobile device’s GPS, media player, audio output, and more.

While less full-featured than Facebook web apps and slower than native smartphone apps, these third-party Facebook mobile platform apps demonstrate how lightweight experiences built on top of the social graph can provide utility.

Here’s how four of the utility app mobile platform launch partners are integrating social and native phone features into their mobile Facebook apps:

HuffPost for Facebook– The Huffington Post’s news reader mobile web app shows a iOS hardware access request to “use your current location”, which allows it surface local news from its Patch network in a “Nearby” tab. This feature will make it especially useful those who want to learn about their surroundings without visiting a dedicated local news site. By pulling a user’s interests and friends, HuffPost can also provide recommendations of articles that friends are reading, Liking, commenting on, or that relate to one’s Likes.

Flixster – This movie reviews Facebook mobile app lets users select to watch film trailers which are instantly opened in the iPhone’s QuickTime player. The app makes it easy to find out what’s in theaters, watch trailers to determine what to see, and then share plans with friends. Flixster also has a native iPhone app so in some cases it will launch that app if installed or open the App Store to download it.